Vinylcyclohexane-based polymers

ABSTRACT

A molding composition comprising a (co)polymer of vinylcyclohexane is disclosed. The copolymer is characterized in having an absolute molecular weight Mw of 100,000 to 450,000 g/mol, polydispersity index of 1 to 3 and maximum melt viscosity of 1000 Pa.s, as measured at 300° C. and at a shear rate of 1000 sec&lt;-1&gt;. The composition is suitable for producing a variety of molded article most notably optical data storage media.

Compared with polycarbonates, which are currently used for theproduction of optical data storage media, polymers based onvinylcyclohexane which exhibit satisfactory mechanical properties have ahigher viscosity at the same temperature over a broad range of low shearrates.

The accurate moulding of pits which are smaller and disposed moreclosely together than those cited in EP-A 317 263 and U.S. Pat. No.4,911,966, and of the grooves which are possible nowadays, is essentialfor high densities of data storage of >5 Gbytes, particularly >10Gbytes.

The method of producing polymers based on vinylcyclohexane which isdescribed in EP-A 317 263 and the use thereof as substrates for opticaldiscs result in a molecular weight which is too low compared with thatwhich would ensure the operationally reliable production thereof(comparative example 1). The mechanical properties of the homopolymersdescribed there are not very suitable for the production of optical datastorage media.

The method described in U.S. Pat. No. 4,911,966 only results inpartially hydrogenated products (<97%), and most of the examplescomprise degrees of hydrogenation of <86%. According to the prior art,partially hydrogenated systems exhibit inadequate transparency (DE-AS 1131 885 (=GB 933 596)). The partially hydrogenated systems which aredisclosed are turbid, and are unsuitable for applications as opticalsubstrates which are penetrated by a laser beam. Partially hydrogenatedsystems also have the disadvantage that their glass transitiontemperature depends on the degree of hydrogenation. In an industrialprocess, an adjustment of the degree of hydrogenation and thus of thethermal properties of the optical substrate can only be reproduciblyimplemented by expending considerable engineering effort and atconsiderable cost.

Moreover, for the most part the partially hydrogenated products whichare cited in U.S. Pat. No. 4,911,966 have a molecular weight which isfar too low for the operationally reliable production of substrates foroptical data storage media.

The aforementioned patent specifications do not mention the quality ofmoulding of pit and groove structures or their existence in principle bymeans of the substrates cited there.

Optimised molecular weights and molecular weight distributions areessential for satisfactory mechanical properties, and at the same timegood melt flow properties are essential for the moulding of pit andgroove structures of high-density optical data storage media.

A molecular weight which is possibly too high can lead to problems withthe moulding of pits and grooves, as a consequence of too high aviscosity.

The substrates according to the present invention, which comprise apolymer based on vinylcyclohexane with a narrow molecular weightdistribution or a mixture thereof with a low molecular weight component,are distinguished by their good level of mechanical properties and bytheir good melt flow properties.

It is thereby possible to produce optical discs in an operationallyreliable manner by injection moulding, and the discs can subsequently behandled without their bending or breaking.

Thinner substrates can be produced which have layer thicknesses lessthan 1.1 mm, of 0.6 mm thickness for example, and which at the same timeexhibit satisfactory mechanical properties.

On account of these properties, the materials can be used verysatisfactorily as substrates for optical data storage media.

Satisfactory mechanical properties are also required for other opticalsubstrates which do not require mechanical indentations in the form ofpits and grooves, for example, and have to be accompanied by a low levelof birefringence, a low moment of inertia, a high level of dimensionalstability when hot, a high modulus of elasticity, low water absorptionand low density. These requirements are also met by the substratesaccording to the invention.

The present invention relates to polymers of vinylcyclohexane with anabsolute molecular weight M_(w) from 100,000 to 450,000 g/mol or amixture thereof with a low molecular weight component with an absolutemolecular weight from 1000 to less than 100,000 g/mol, wherein themolecular weight distribution is characterised by a polydispersity index(PDI=M_(w)/M_(n)) of 1 to 3 and the maximum melt viscosity is 1000 Pa·s,as measured at 300° C. and at a shear rate of 1000 sec⁻¹.

Any oligomeric fraction with a molecular weight M_(w) of up to 3000g/mol which may possibly be present is not taken into account in thecalculation of the polydispersivity index.

Any oligomeric fraction with a molecular weight of up to 3000 g/molwhich may be present amounts to less than 5% of the weight of thepolymer.

The molecular weight M_(w) of the high molecular weight polymer(homopolymer) preferably ranges from 200,000 to 450,000 gmol⁻¹, andranges in particular from 200,000 to 400,000 gmol⁻¹.

The molecular weight M_(w) of a high molecular weight copolymer or blockpolymer preferably ranges from 100,000 to 400,000 gmol⁻¹, and ranges inparticular from 100,000 to 250,000 gmol⁻¹.

The molecular weight M_(w) of the low molecular weight componentgenerally ranges from 1000 to 100,000 gmol⁻¹, preferably from 7000 to90,000 gmol⁻¹, most preferably from 10,000 to 90,000 gmol⁻¹.

The molecular weight distribution of the respective component ischaracterised by a polydispersity index (PDI=Mw/Mn) from 1 to 3.

In the case of mixtures, the proportion of low molecular weightcomponent with respect to the weight of the mixture of high molecularweight and low molecular weight polymers generally amounts to up to 70%by weight, preferably 5 to 60% by weight, most preferably 10 to 50% byweight.

A polymer based on vinylcyclohexane is preferred both for the highmolecular weight and for the low molecular weight component. Thispolymer comprises a recurring structural unit of formula (I)

wherein

R¹ and R², independently of each other, denote hydrogen or a C₁-C₆alkyl, preferably a C₁-C₄ alkyl,

R³ and R⁴, independently of each other, represent hydrogen or a C₁-C₆alkyl, preferably a C₁-C₄ alkyl, particularly methyl and/or ethyl, or R³and R⁴ jointly represent an alkylene, preferably a C₃ or C₄ alkylene(comprising a condensed-on 5- or 6-membered cycloaliphatic ring),

R⁵ represents hydrogen or a C₁-C₆ alkyl, preferably a C₁-C₄ alkyl,

R¹, R² and R³, independently of each other, represent hydrogen or methylin particular.

Apart from stereoregular head-to-tail linkages, the concatenation of theabove structural units can comprise a small proportion of head-to-headlinkages. The vinylcyclohexane-based polymer can be branched viacentres, and can have a star configuration structure for example.

Comonomers can be contained in an amount which generally ranges from 0to 80% by weight, preferably from 0 to 60% by weight, most preferablyfrom 0 to 40% by weight, with respect to the finished polymer. Polymersare preferred which comprise recurring structural units of formula (I)and which are formed from one monomer or from a mixture of monomers.

The following substances can preferably be used as comonomers andincorporated in the polymer during the polymerisation of the startingpolymer (a polystyrene which is optionally substituted): olefines whichgenerally comprise 2 to 10 C atoms, such as ethylene, propylene,isoprene, isobutylene or butadiene for example, C₁-C₈, preferably C₁-C₄alkyl esters of acrylic or methacrylic acid, unsaturated cycloaliphatichydrocarbons, e.g. cyclopentadiene, cyclohexene, cyclohexadiene,norbomene which is optionally substituted, dicyclopentadiene,dihydrocyclopentadiene, tetracyclodecene which is optionallysubstituted, styrenes with alkylated nuclei, α-methylstyrene,divinylbenzene, vinyl esters, vinylic acids, vinyl ethers, vinylacetate, vinyl cyanides such as acrylonitrile or methacrylonitrile,maleic anhydride, and mixtures of these monomers.

The polymers can have a linear chain structure, or can also comprisebranching sites due to co-units (e.g. graft copolymers). The branchingcentres may comprise star configuration polymers or branched polymers.The polymers according to the invention can comprise other forms of whatis a primary, secondary, tertiary or optionally a quaternary polymerstructure, such as a helix, a double helix, a folded sheet, etc., ormixtures of these structures.

Homopolymers formed from a monomer corresponding to formula (I) areparticularly preferred.

Polymers which are particularly preferred for the high molecular weightcomponent include homopolymers of a monomer corresponding to formula(I), most preferably hydrogenated styrene-isoprene polymers,particularly block copolymers, and can be used either on their own or asa mixture.

Polymers which are particularly preferred for the low molecular weightcomponent include homopolymers of a monomer corresponding to formula(I), (block) copolymers, most preferably hydrogenated styrene-isoprenepolymers, particularly hydrogenated styrene-isoprene polymers whichcomprise 3 to 8, preferably 3 to 5, radial members. The low molecularweight component can be present either as one polymer or as mixtures ofsaid polymers.

The vinylcyclohexane-based polymers can have an atactic, a predominantlysyndiotactic or a predominantly isotactic diad configuration.

Amorphous substrates are also preferred which comprise a predominantlysyndiotactic configuration of the vinylcyclohexane units and which arecharacterised in that the amount of diads is greater than 50.1% and lessthan 74%, most preferably greater than 52% and less than 70%.

Methods of elucidating the microstructure by means of ¹³C—¹H correlationspectroscopy of the methylene carbon atoms of a polymer backbone aregenerally known and are described by A. M. P. Ros and O. Sudmeijer (A.M. P. Ros, O. Sudmeijer, Int. J. Polym. Anal. Charakt. (1997), 4, 39)for example.

The signals of crystalline isotactic and syndiotacticpolyvinylcyclohexane are determined by means of two-dimensional NMRspectrometry. In the 2D CH correlation spectrum, the methylene carbonatom (in the polymer backbone) of isotactic polyvinylcyclohexane splitsinto two separate proton signals, and indicates a purely isotactic diadconfiguration. Syndiotactic polyvinylcyclohexane, on the other hand,only exhibits one signal for the C 1 carbon atom in the 2D CHcorrelation spectrum. The amorphous syndiotactic-richpolyvinylcyclohexane according to the invention exhibits an integralexcess of intensity of syndiotactic diads compared with the isotacticdiad configuration.

VCH polymers are produced by polymerising derivatives of styrene withcorresponding monomers, by a radical, anionic or cationic mechanism, orby means of metal complex initiators or catalysts, and by subsequentlycompletely or partially hydrogenating the unsaturated aromatic bonds(see, for example, WO 94/21694, EP-A 322 731).

Polymers based on vinylcyclohexane are produced in particular by thehydrogenation of styrene derivatives which have been polymerised by ananionic or radical mechanism. The polymers according to the inventioncan comprise bimodal or optionally multimodal distributions over therange of polydispersity considered.

One skilled in the art in the field of anionic and radicalpolymerisation is aware that the polydispersities of prepolymers can beadjusted between 1 and 3 (Braun, D., Praktikum der makromolekularenorganischen Chemie, revised, expanded edition, Heidelberg, Huethig1979).

The absolute (weight average) molecular weights Mw of the hydrogenatedproducts are determined by light scattering. The absolute (numberaverage) molecular weights Mn are determined by membrane osmosis (vapourpressure osmosis). Another method of characterising the molecular weightdistribution by polydispersity is the measurement of the relativemolecular weights Mw and Mn by gel permeation chromatography.

The process generally results in practically complete hydrogenation ofthe aromatic units. As a rule, the degree of hydrogenation is ≧80%,preferably ≧90%, most preferably >99% to 100%. The degree ofhydrogenation can be determined by NMR or UV spectrometry, for example.

The melt viscosity is determined by the oscillation method, by means ofa melt viscometer of plate and cone construction. The viscosity dependson the shear rate (angular frequency), and the viscosity at 300° C. and1000 sec⁻¹ of the polymers or mixtures according to the invention isgenerally up to 1000 Pa·s, and preferably ranges from 5 to 500 Pa·s,most preferably from 10 to 200 Pa·s.

The starting polymers are generally known (e.g. WO 94/21 694).

Polymerisation can be conducted continuously, semi-continuously orbatch-wise.

The amount of catalyst used for hydrogenation depends on the processemployed; the latter can be carried out continuously, semi-continuouslyor batch-wise.

In a batch process, the ratio of catalyst to polymer is generally0.3-0001, preferably 0.2-0.005, most preferably 0.15-0.01.

The polymer concentrations with respect to the total weight of solventand polymer generally range from 80 to 1, preferably 50 to 10,particularly 40 to 15% by weight.

The starting polymer is hydrogenated by methods which are generallyknown (e.g. WO 94/21 694, WO 96/34 895, EP-A-322 731). A multiplicity ofknown hydrogenation catalysts can be used as catalysts. Examples ofpreferred metal catalysts are cited in WO 94/21 694 or WO 96/34 896. Anycatalyst which is known for hydrogenation reactions can be used.Suitable catalysts include those with a large surface area (e.g. 100-600m²/g) and a small average pore diameter (e.g. 20-500 Å). Other suitablecatalysts include those with a small surface area (e.g. ≧10 m²/g) andlarge average pore diameters which are characterised in that 98% of thepore volume comprises pores with pore diameters larger than 600 Å (e.g.about 1000-4000 Å) (see, for example, U.S. Pat. No. 5,654,253, U.S. Pat.No. 5,612,422, JP-A 03076706). Raney nickel, nickel on silica or onsilica/alumina, nickel on carbon as a support, and/or noble metalcatalysts e.g. Pt, Ru, Rh, Pd, are used in particular.

The reaction is generally conducted at temperatures between 0 and 500°C., preferably between 20 and 250° C., particularly between 60 and 200°C.

The solvents which are customarily used for hydrogenation reactions aredescribed in DE-AS 1 131 885 for example (see above).

The reaction is generally conducted at pressures from 1 bar to 1000 bar,preferably from 20 to 300 bar, particularly from 40 to 200 bar.

The vinylcyclohexane-based polymers or copolymers according to theinvention are of excellent suitability for the production of opticaldata storage media, preferably those with densities of data storage >5Gbyte, particularly >10 Gbyte, with respect to a disc of 120 mmdiameter.

Additives, such as stabilisers and demoulding agents for example, can beadded to the vinylcyclohexane-based polymers or (block) copolymers.

Examples of optical data storage media include:

magneto-optical disc (MO disc)

mini-disc (MD)

ASMO (MO-7) (“advanced storage magneto-optic”)

DVR (12 Gbyte disc)

MAMMOS (“magnetic amplifying magneto-optical system”)

SIL and MSR (“solid immersion lens” and “magnetic super-resolution”)

CD-ROM (read only memory)

CD, CD-R (recordable), CD-RW (rewritable), CD-I (interactive), photo-CDsuper audio CD

DVD, DVD-R (recordable), DVD-RAM (random access memory);

DVD=digital versatile disc

DVD-RW (rewritable)

PC+RW (phase change and rewritable)

MMVF (multimedia video file system).

Moreover, due to their outstanding optical properties the polymersaccording to the invention are particularly suitable for the productionof optical materials. e.g. for lenses, prisms, mirrors, colour filters,etc., and are also suitable as media for holographic images (e.g. forcheque cards, credit cards, passes, and for three-dimensionalholographic images). The materials can be used as transparent media onwhich three-dimensional structures can be inscribed, e.g.three-dimensional structures from focused coherent radiation (LASER),and can be used in particular as three-dimensional data storage media orfor the three-dimensional imaging of objects.

EXAMPLES Production Examples 1-4 Hydrogenated Polystyrene (h-PS)

A 40 litre autoclave was flushed with inert gas (nitrogen). The polymersolution and catalyst were added (Table 1). After closing the autoclave,it was repeatedly pressurised with an inert gas and was then pressurisedwith hydrogen. After releasing the pressure, the respective hydrogenpressure was set and the batch was heated with stirring to thecorresponding reaction temperature. After the absorption of hydrogen hadcommenced, the reaction pressure was held constant. The reaction timewas defined as the period from heating up the batch until the time atwhich the hydrogen atoms approached their saturation value.

After completion of the reaction, the polymer solution was filtered. Thestabiliser was added, and the product was freed from solvent at 240° C.and was processed further as a granular material (Examples 1 to 4, Table1).

The molecular weights listed in Table 2 can be achieved by the reactionconditions employed, particularly the temperature (Table 1), and by thesubsequent work-up conditions (temperature of evaporation of solvent,type of stabiliser and the concentration thereof).

Example 5 Production of Poly(styrene-block-co-isoprene)

These syntheses were carried out using standard inert gas techniques.138 kg abs. cyclohexane were placed in a 250 litre reactor. 6.3 kg abs.styrene were introduced into the reactor at room temperature. Thetemperature was raised to 55° C. and 102 ml (0.255 mol) n-butyllithium(a 23% solution in n-hexane) were introduced into the reactor. Thereaction mixture was heated to 70° C. and was stirred for 30 minutes.

1.4 kg abs. isoprene and 6.3 kg abs. styrene were simultaneouslyintroduced into the reactor. The mixture was held at 70° C. for 2 hours.The reaction solution was cooled to room temperature and a solution of10 g 2-propanol in 500 g cyclohexane was added. The polymer solution wasconcentrated to 16.6% by weight at 40 to 45° C. under vacuum.

Example 6 Production of Hydrogenated Poly(styrene-block-co-isoprene)

22 kg of the polymer solution (Example 5) were transferred undernitrogen to a 40 litre autoclave. After adding 421.5 g Ni 5 136 P(Engelhard), the autoclave was repeatedly pressurised with nitrogen andhydrogen. The reaction solution was heated at 100 bar to 170° C. Afterthe heat-up phase, the reaction was conducted at 150 bar, as controlledby an automated pressure device, until constant pressure was achieved,and the batch was stirred for a further two hours.

The catalyst was filtered from the polymer solution. The polymersolution was stabilised with 4000 ppm Irganox XP 420 FF, was freed fromsolvent at 240° C. and was processed further as a granular material.

Example 7 Production of Star ConfigurationPoly(styrene-block-co-isoprene)

1200 g cyclohexane, 800 g methyl-tert.-butyl ether and styrene (350 g,3.37 mol) were transferred into a 5 litre steel autoclave. Butyllithium(1.24 g, 19.3 mmol) was added to the solution with stirring at roomtemperature (25° C.). Polymerisation was conducted for 1.5 hours at thistemperature. Thereafter, isoprene (53 g, 0.77 mmol) was added to thepolymer solution. After 1.5 hours, tetramethoxysilane (0.61 g, 4 mmol)was added as a 7.5% by weight solution in cyclohexane to the blockcopolymer solution. Concatenation to form the star configuration polymerwas effected at 80° C. for 3 hours. Thereafter, 5 ml isopropanol wereadded.

Example 8 Production of Hydrogenated Star ConfigurationPoly(styrene-block-co-isoprene)

Nickel on silica/alumina (Aldrich) was added to the polymer solution(Example 7), which was then transferred to a 5 litre autoclave. Thelatter was repeatedly rendered inert with nitrogen. Afterdepressurisation, the hydrogen pressure was set at 100 bar and the batchwas heated to 180° C. and held at this temperature for 6 hours. Eachtime the pressure fell to 80 bar, it was increased to 100 bar again.After completion of the reaction, the batch was cooled to roomtemperature, the catalyst was separated from the polymer solution byfiltration, and the polymer was dried under vacuum.

Example 9 Production of a Blend of Hydrogenated Polystyrene andHydrogenated, Star Configuration Poly(styrene-block-co-isoprene)

The polymer (Example 8) was dissolved, as a 20% solution, incyclohexane/methyl-tert.-butyl ether in a ratio of 2/1, was treated withthe stabiliser Irganox XP 420 FF and was mixed with a solution of thehydrogenated polystyrene (Example 4) in a ratio of polymers of 50/50.The solvent was removed under vacuum and the dried polymer was processedin an extruder to form granules.

The granules were processed to form moulded blanks by a CD injectionmoulding process (Table 4).

TABLE 1 Hydrogenation of polystyrene Degree of Weight of Weight ofReaction Hydrogen Reaction hydrogen- Example polymer²⁾ Solvent catalysttemp. pressure time ation¹⁾ Stabiliser No. (kg) (liters) (g) (° C.)(bar) (hours) (%) (ppm) 1 5.0 151 625³⁾ 180 100 9.7 100 2500 cyclo-Irganox* hexane B 561 101 methyl-t- butyl ether 2 5.0 151 625³⁾ 160 10016.5 100 2500 cyclo- Irganox* hexane B 561 101 methyl-t- butyl ether 34.8 151 625⁴⁾ 160 100 17.5 100 4000 cyclo- Irganox* hexane XP420 9.11 FFmethyl-t- butyl ether 4 4.8 151 625⁴⁾ 160 100 19 100 Irganox* cyclo- XP420 hexane FF 1.11 methyl-t- butyl ether ¹⁾determied by ¹H NMRspectrometry ²⁾polystrene Type 158 k, transparent, Mw 280,000 g/mol,BASF AG, Ludwigshafen, Germany ³⁾Ni/SiO₂/Al₂O₃, 64-67% nickel, Aldrich⁴⁾Ni/SiO₂/Al₂O₃, Ni-5136 P, Engelhard, De Meern, Holland *Thestabilisers were commercial products of Ciba, Basle, Switzerland.

TABLE 2 Molecular weights Mn, Mw; PDI; and pit or groove moulding whilstsimultaneously complying with the mechanical requirements for CDinjection moulding Average Average Maximum process- molecular molecularing temperature at Mould Cracks in optical weight Mn¹⁾ weight Mw²⁾Polydispersity die outlet temperature substrate Pit depth³⁾ Example No.(10³ g/mol) (10³ g/ mol) PDI (° C.) (° C.) (+/−) (mm) 1 A 91.2 191.5 2.1330 85 + 92 comparative 2 B 109.8 238.4 2.2 315 70 − 110 according tothe invention 3 A 107.3 267.2 2.5 335 85 − 82 according to the invention4 C 108.0 259.0 2.4 350 85 − 75 according to the invention 6 C 96.8121.3  1.25 315 75 − 80 according to the invention 4 A 108.0 259.0 2.4320 100 − 122 according to the invention 9 A⁵⁾ 54.5⁴⁾/108.0 62.0⁴⁾/259.01.1/2.4 320 100 − 140 Mixture according to the invention A = Standarddigital versatile disc die, substrate produced by means of Nestal Disjet600 B = Standard compact disc die, substrate produced by means of NestalDisjet 600 C = High density digital versatile die with 93 mm pit depthas measured PDI = Polydispersity ¹⁾Absolute molecular weights Mn fromthe measured correlation of the GPC values of the vinylcyclohexane-basedpolymers with molecular weights determined by membrane osmosis²⁾Absolute molecular weights Mw from the measured correlation of the GPCvalues of the vinylcyclohexane-based polymers with molecular weightsdetermined by light scattering ³⁾determined by scanning force microscopy(AFM) ⁴⁾molecular weights Mn and Mw of the prepolymer as measured by GPC⁵⁾50/50 blend

Various pit depths can be obtained in an injection moulding or injectionembossing process depending on the depths of the pits and grooves of thedie used. The pit depth or groove depth can be varied by adjustments tothe apparatus, by the mould temperature and by the melting temperatureof the polymer.

Example 1A (Table 2) illustrates good pit moulding of thevinylcyclohexane-based polymer. However, the Substrates of optical datastorage media which were produced by injection moulding comprisedfissures (termed cracks or microcracks). The materials which arecharacterised in Examples 2B and 3C could be produced without theoccurrence of cracks or microcracks. The vinylcyclohexane-based polymersaccording to the invention constitute ideal optical substrates, which atthe same time facilitate good pit or groove moulding at low dietemperatures without the occurrence of cracks.

Both Example 4C (homopolymer) and Example 6C (copolymer) illustrate goodpit replication (75 nm/80 nm) at low mould temperatures, without theformation of cracks. Moreover, Example 6C (copolymer) illustratesexcellent pit replication at low processing and die temperatures.

Example 9A (a blend of a high molecular weight polymer and a lowmolecular weight component) also illustrates excellent pit replicationwithout crack formation.

The CD substrates according to the invention can be produced withoutcracks with enhanced operational reliability compared with example 1 A.

What is claimed is:
 1. Polymers of vinylcyclohexane with an absoluteweight average molecular weight M_(w) from 100,000 to 450,000 g/molcombined with a low molecular weight component based on vinylcyclohexanewith an absolute weight average molecular weight from 1000 to less than100,000 g/mol, wherein the molecular weight distribution ischaracterized by a polydispersity index of 1 to 3 and the maximum meltviscosity is 1000 Pa·s, as measured at 300° C. and at a shear rate of1000 sec⁻¹.
 2. The mixture according to claim 1, containing, as avinylcyclohexane-based polymer, a polymer comprising a recurringstructural unit of

formula (I) Wherein R¹ and R², independently of each other, denotehydrogen or a C₁-C₆ alkyl, R³ and R⁴, independently of each other,denote hydrogen or a C₁-C₆ alkyl or jointly represent an alkylene, R⁵represents hydrogen or a C₁-C₆ alkyl, and optionally containing at leastone comonomer selected from the group consisting of olefins containing 2to 10 C atoms, C₁-C4 alkyl esters of acrylic acid, alkyl esters ofmethacrylic acid, unsaturated cycloaliphatic hydrocarbons,tetracyclodecenes which are optionally substituted, divinylbenzene,vinyl esters, vinyl acids, vinyl actates and vinyl cyanides.
 3. Themixture according to claim 1, wherein the high molecular weightcomponents exist as homopolymers, copolymers or block copolymers.
 4. Themixture according to claim 1, wherein the proportion of low molecularweight component with respect to the weight of the mixture of high andlow molecular weight components amounts to up to 70% by weight. 5.Moldings according to claim
 1. 6. An optical substrate containing themixture according to claim
 1. 7. A molding composition comprising a(co)polymer of vinylcyclohexane having an absolute molecular weightM_(w) of 100,000 to 450,000 g/mol and at least one low molecular weightpolymer of vinylcyclohexane having an absolute molecular weight of 1,000to less than 1000,000 g/mol, wherein the composition has polydispersityindex of 1 to 3 and maximum melt viscosity of 1,000 Pa·s, as measured at300° C. and at a shear rate of 1,000 sec⁻¹.
 8. The composition of claim7 wherein (co)polymer contains the recurring structural unit of formula

wherein R¹ and R², independently of each other, denote hydrogen or aC₁-C₆ alkyl, R³ and R⁴, independently of each other, denote hydrogen ora C₁-C₆ alkyl, or jointly represent an alkylene, R⁵ represents hydrogenor a C₁-C₆ alkyl.
 9. The composition of claim 7 wherein the (co)polymeris the product of polymerization of at least one comonomer selected fromthe group consisting of olefins containing 2 to 10 C atoms, C₁-C₄ alkylesters of acrylic acid, C₁-C₄ alkyl esters of methacrylic acid,unsaturated cycloaliphatic hydrocarbons, tetracyclododecenes,divinylbenzene, vinyl esters, vinyl acids, vinyl ethers, vinyl acetatesand vinyl cyanides.
 10. The composition of claim 7 wherein (co)polymeris a block copolymer.
 11. The composition of claim 7 wherein the lowmolecular weight polymer of vinylcyclohexane is present in an amount ofup to 70% relative to the weight of the composition.
 12. An opticalmaterial comprising the composition of claim
 7. 13. The optical materialof claim 12 wherein the optical material is an optical data storagemedium.
 14. A molded article comprising the composition of claim 7.